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Compatibility50: Install objc_getClass hook only in main executable #30866

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Merged
merged 1 commit into from
Apr 8, 2020
Merged

Compatibility50: Install objc_getClass hook only in main executable #30866

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23 changes: 23 additions & 0 deletions stdlib/toolchain/Compatibility50/Overrides.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@
#include "../../public/runtime/CompatibilityOverride.h"

#include <dlfcn.h>
#include <mach-o/dyld.h>
#include <mach-o/getsect.h>

using namespace swift;

Expand Down Expand Up @@ -70,8 +72,29 @@ getObjCClassByMangledName_untrusted(const char * _Nonnull typeName,
return NO;
}

#if __POINTER_WIDTH__ == 64
using mach_header_platform = mach_header_64;
#else
using mach_header_platform = mach_header;
#endif

__attribute__((constructor))
static void installGetClassHook_untrusted() {
// swiftCompatibility* might be linked into multiple dynamic libraries because
// of build system reasons, but the copy in the main executable is the only
// one that should count. Bail early unless we're running out of the main
// executable.
//
// Newer versions of dyld add additional API that can determine this more
// efficiently, but we have to support back to OS X 10.9/iOS 7, so dladdr
// is the only API that reaches back that far.
Dl_info dlinfo;
if (dladdr((const void*)(uintptr_t)installGetClassHook_untrusted, &dlinfo) == 0)
return;
auto machHeader = (const mach_header_platform *)dlinfo.dli_fbase;
if (machHeader->filetype != MH_EXECUTE)
return;

// FIXME: delete this #if and dlsym once we don't
// need to build with older libobjc headers
#if !OBJC_GETCLASSHOOK_DEFINED
Expand Down